The invention relates to a withdrawal system according to the preamble of claim 1.
This type of withdrawal system is generally used to fill and empty containers, in particular barrels, that are filled with liquid chemicals. To fill or empty the container, the container has an immersion pipe that is typically mounted in the cover of the container and from there projects into the interior of the container. A withdrawal head is secured to the immersion pipe to enable liquid to be fed into or withdrawn from the container. This immersion pipe is connected via pipes to a pump, by means of which liquid is pumped into or out of the container.
A withdrawal system of this type is known from DE 10 2013 110 020 A1. In this withdrawal system, a switch is provided on the withdrawal head that signals whether or not the withdrawal head is attached in an intended position on the immersion pipe. This switch thus detects incorrect attachments of the withdrawal head to the immersion pipe, which are indicated by an alarm indication or the like. The operating personnel can thereby detect the unsatisfactory attachment and then undertake corrective measures.
A problem associated with withdrawal systems of this type is that even an initially correct connection between immersion pipe and withdrawal head can be loosened or detached by mechanical disturbing influences and the like and this can go undetected or be detected by such a switch only if liquid can escape from the container via the loosened closure. An occurrence of such problems is especially a concern if the withdrawal system of the container is connected to a diaphragm pump for the purpose of withdrawing or adding liquid. Membrane pumps of this type generate vibrations that are transmitted via the hose or piping system to the withdrawal system. The threaded connection of the withdrawal head to the immersion pipe can be loosened by these vibrations. As a result, this connection will leak, and liquid can escape in an uncontrolled manner. In order to correct such faults, the operation of the withdrawal system must be interrupted, and the connection between withdrawal head and immersion pipe must be correctly re-established, which is time-consuming and results in correspondingly long down-times.